Wet-strengthened carboxylated cellulosic materials containing melamine formaldehyde resin and a process for preparing the same

ABSTRACT

A method of preparing fibrous cellulosic materials containing resins such as trimethylolmelamine so as to improve bonding between fibers and the wet state and conditioned state resistances, said method being one in which cellulose fibers are oxidized with an alkali metal periodate to form aldehyde groups in the 2 and 3 positions, and the aldehyde containing cellulose fibers are then further oxidized with an alkali metal chlorite to form carboxyl groups in the 2 and 3 positions, and the resin precursor is reacted in acidic medium and is mainly retained by an ion exchange mechanism on cellulose fibers, those fibers then being used on paper or cardboard machines; and the new products so obtained.

Ffi XQR 395579965 unueu mates l'awlll us] 3,657,066

Cherie et a1. Apr. 18, 1972 54] WET-STRENGTHENED OTHER PUBLICATIONS CARBOXYLATED CELLULOSIC MATERIALS CONTAINING MELAMINE ifgg grgggt it %3?f332 FORMALDEHYDE RESIN AND A Landes and Maxwell. A Study of the Melamine Resin Process PROCESS FOR PREPARING THE SAME for Producing Wet Strength Paper. Aug. 9 1945. Tappi pp.

51-60 [72] Inventors: Marcel Cherie, True Marcel Benoit,

Grenoble} Jean Pierre Q v Lenomeau Primary Examiner-5. Leon Bashore Fleaunvlua Momtbommot Jean AssistantExaminer-Richard H.Anderson Francis Lafaye 30 we Edonard Vomamr An0rnerWmv J. Foley, John W. Kane, Jr., J. A. Wevgandt Grenoble 38, all of France and L Faigus Filed: Dec. 29, 1969 1 1 1 ABSTRACT 21 App1.No.. 88,98

A method of preparing fibrous cellulosic materials containing resins such as trimethylolmelamine so as to improve bonding [52] "162/l66'8/108"5*8/l162* between fibers and the wet state and conditioned state re- 162/182 sistances, said method being one in which cellulose fibers are [5 Cl. Oxidized ,l'th an metal periOdute to form aldgh dc Field of Search 18178) C; groups in the 2 and 3 positions. and the aldehyde containing 8/1162 117/1 5 cellulose fibers are then further oxidized with an alkali metal chlorite to form carboxyl groups in the 2 and 3 positions, and [56] References cued the resin precursor is reacted in acidic medium and is mainly UNITED STATES PATENTS retained by an ion exchange mechanism on cellulose fibers. those fibers then being used on paper or cardboard machines: 2,991.194 7/1961 Camrron ..117/155 L and the new products so 0bminc 2.999.789 9/1961 Quinn ..162/166 3.481048 12/1969 Devzeman ..260/67.6 3 Claims, N0 Drawings WET-STRENGTHENED CARBOXYLA'I'ED CELLULOSIC MATERIALS CONTAINING MELAMINE FORMALDEHYDE RESIN AND A PROCESS FOR PREPARING THE SAME BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to the field of cellulose compounds and paper pastes, and concerns, more particularly, a method of producing cellulose compounds having fixed thereon certain melamine-formaldehyde resin precursors, and the various new articles of manufacture produced thereby.

In one aspect, this invention relates to a method of producing oxidized cellulose fibers on which are retained especially melamine-formaldehyde resin precursors so as to reinforce bonding between fibers of papers and other cellulosic products made from such fibers. In another aspect, this invention relates to the retention of melamine-formaldehyde resin precursors by sulfuric esters of cellulose.

2. Description of Prior Art Heretofore, from the data of technical literature and patents, the ability of cellulose derivatives to retain high rates of melamineformaldehyde resins, so as to improve bonding between cellulose fibers to obtain paper-like products was not known.

Therefore, the main object of this invention is to provide methods of retaining melamine-formaldehyde type resins on cellulose, many cellulose derivatives and other fiber constituents.

SUMMARY OF THE lNVENTION According to the invention, it has been now found that resin precursors of melamine-formaldehyde resins could be retained on suitably oxidized fibers. The influence of oxidation is predominant because the amount of the retained resin precursor is increased by increasing the carboxyl rate.

According to the invention, there is provided a method of preparing cellulose fibers retaining resin precursors so as to improve bonding between fibers and the wet state and conditioned state resistances, said resin precursors being especially selected from the group comprising melamine-formaldehyde resin precursors in which cellulose fibers are submitted to an oxidation resulting in creating carboxyl groups in 2, 3 or 6 position, and, on oxycelluloses obtained thereby, the resin precursor is reacted in acidic medium and is mainly retained by an ion exchange mechanism on cellulose fibers, those fibers being used on paper or cardboard machines.

As an example, only the case of an oxidation on 2, 3 position of cellulose will be considered; cellulose fibers may be regenerated cellulose fibers, for example those of regenerated viscose.

The oxidation of cellulose may be carried out by sodium metaperiodate at room temperature; in this case, it leads to the formation of aldehydes in 2 and 3 positions. A further oxidation by sodium chlorite converts carbonyl groups into carboxyl groups. Oxidation through N leads to aldehyde groups in 6 position.

Laboratory studies of exchanges made on diversely oxidated fibers is carried out generally in a standardized apparatus for carboxyl dosage. The resin precursor is dissolved in hydrochloric acid and diluted. Previously defibered and demineralized samples are taken and the resin precursor solution is added in small increments, the final percentage of used resin precursor reacting about 2 g. per 100 g. cellulose.

The pH of the resin precursor solution may be from 6,5 to about 3; the reaction will be preferably realized at a pH near 6 so as to obtain a maximum ion exchange. The influence of extra ions will be as much as possible eliminated; indeed, when H ions are accompanied with extra-cation, the retention of same may be made instead of the resin precursor.

The melamine-formaldehyde resin precursor is retained by ion exchange on carboxyls according to the following mechanism:

1. formation of a cation in acidic medium:

M H MH M trimethylolmelamine 2. Exchange with H ions of acidic groups of cellulose:

Cell'COOI-l MH Cell-COOMH H It should be noted that this mechanism would be similar with carboxyl groups in 6 position as well as with such groups as SO H. It is very important to remark that the resin precursor should have, by association with H ions, a strong positive charge so as to be in the best ion exchange conditions.

In addition to this fixation through ion exchange, there may exist a fixation through hydrogen bonds and a fixation due to purely mechanical action, for example the filtration of the colloid through very fine mesh of the forming sheet. These conclusions result from tests carried out with native cellulose fibers and cellulose regenerated from viscose, from which oxycelluloses have been prepared.

According to this invention, there is also provided a method of producing sulfuric esters of cellulose to which will be retained resin precursors selected from the group comprising melamine-formaldehyde resin precursors in which the reaction on cellulose fibers is made in alcoholic medium, in the presence of concentrated sulfuric acid so as to obtain the ester and the resin precursor is made to react in an acidic medium so as to make the resin precursor/sulfuric cellulose ester exchange.

The following embodiments are only given as an illustration of this invention, without any limitation.

EXAMPLE 1 Retention of resin precursor at constant pH Polynosic fibers (regenerated cellulose for paper-making applications) are treated by sodium metaperiodate 0.1 Molar, at room temperature and in darkness.

Dialdehydes are converted into diacids by a sodium chlorite solution made acidic at pH 3.

As a confirmation of the influence of carboxyl groups, aldehyde groups are converted into alcohol groups through treatment by a sodium borohydride solution.

[on exchange is conducted in the following manner: 600 mg of trimethylolmelamine (known under trademark PAREZ 607) are dissolved within 5 ml. of hydrochloric acid at 16.5 g./l., then diluted immediately to 2 l with deionized water. Exchange is made in the carboxyl apparatus, on samples of about 1 g., previously defibered and dirnineralized. The thus prepared trimethylolmelamirze solution at a concentration of 300 mg./l. is added in small increments of 25 or 50 ml.; after filtration, the pH of each cut is measured.

The obtained results are collected in tables 1 through V.

TABLE I lon exchange resin precursor-viscose cellulose as a blank 1.9

millequivalents of CHO/ g. to 2 millequivalents of COOH/IOO g.

Retention Introduced Retained resin resin precursor, precursor,

millimilli- Ini- Filgrams/ grams/ Exchanged tial trate gram of gram 01 Pervolurne (mL) pH pH paste paste cent TABLE ll From these results, it appears very well that the retention of melamine-formaldehyde resin precursor is clearly increased by increasing the carboxyl rate.

5 EXAMPLE 2 Viscose fibers oxidated with metaperiodate 2 millequivalents of COOH/lOO g. and lOl millequivalents ofCHO/lOO g.

Resin precursor retention against pH of the exchange solution Rmmkm The used resin precursor is supplied in solution; its pH is near 6 after dilution. Exchanges are carried out as in Example resin resin l, the pH of exchange solution being decreased by adding precursor, precursor. I mm mm hydrochloric acid. F l 1 1"; c 4 u m I. Results are presented in Table Vl which shows the 1m- 4X: lilllfii( llll Til .1 'l'tllll (l 'rlllll O (lt vulmmt (mm pH L paste cum portance of initial pH of the res1n precursor solution during 3.211 3. 3-1 17.1 1.77 10.3 exchange 2 3. 411 31. 1 2.4112 7.25 3. 52 3. 51 111. s 2.11 5.11 TABLE VI 3.52 3152 1' .5 3.15 4.1;

Resin precursor retention against pH TABLE Ill (Viscose suroxidated with chlorite: 79 millequivalents COOH/ l 00 g. Viscose fibers oxidated w1th metapenodate, suroxidated w1th chlorite 67.8 millequivalents of coon/100 g. ggfl 152 3 precursor. Retained milligrams! resin gram of precursor, Retention paste millilntro pH (exchanged grams/ duced Retained of the volun1e= grain Perresm resln Initial pH filtrate 100 cn1. of paste cent precursor, precursor, millimilli- 3.9 2 15. .1 37.5 Ini- Filgrams! grams] 3. 74 18. 11. 711. 7 Exchanged tial trate gram of grant of 3. 6'2 18. 22 14. -15 711.3 volume (ml.) p11 pH paste pa te 3.5 18. 32 13.5 71.5 3.5 18.32 13.5 71.5 3% 2. 96 16.8 10.21 2. as 13.1 10.11 60.3 100 3. 32 3.1 31.1 17.1 1. 82 18.3 9. 5 52 150 3. 41s 3. 25 51. 2 24.13 1.12 13. 3 3 16.4 200 3.28 3.12 117.1 37.6 250 3.33 3.12 88.8 40. 87

EXAMPLE 3 TABLE W 40 Cellulose treated w1th H 80 The assay of SO H groups is carried out with gravimetry, and also through exchange with zinc acetate. chlorite 140 millequivalents ofCOOi-i/ 100 g Results of exchanges and of resin precursor retention on 45 cellulose esters are collected in Table Vll.

Viscose fibers oxidated with metaperiodate, suroxidated with I t Retention TABLE VI} n roduced Retained Exchange rate=33.6 millequivalents/IOO grams resin resin precursor, precursor, Intromillimilli- 5O dueed Ini- Filgrams/ grams/ res1r1 Exchanged tial trate gram of gram 01 Perpre volume (ml.) pH pH paste paste cent Volume of pH cursor Retenexchanged Initial of the (per tion. 150 3. 43 3.15 43.3 26.10 60.5 Weight of paste solution pH filtrate cent) percent 250 3. 56 3. 30 77 37. 19 48. 3 a

1 gram ..{g* 3.31 1.5 37.5 50+ 0111. 2.96 i511 cmk i 2.96 i 3 TA V 50 ms. 2. 96

Do {50 cm 2. 95 4. 5 85 Viscose fibers ox dated w1th metaperiodate 101 ig fi'fi 313g millequlvalents of 60 0 100 cm a 3- 04 9 4 CHO/ 100 grams reduced with sodium borohydride 1.46

mmequivalems According to the results of Table VII, it appears that GHQ/100 g melamine-formaldehyde resin precursor may be, in suitable condmons, retalned almost quantitauvely by ten exchange.

I t Retention EXAMPLE 4 11 1'0- duced Retained precu r si g recu'fil, 70 Printing of cellulose sheets and retention of resin ml m u 1 I s 1 F s g ms! The operatmg conditions are as follows: prrntmg of sheets 1n izgliiiiigiiigl-l iii? "Si; ii si iflsti 55.; the Rapid Kothen formette," drying under vacuum at 90 C. 50 3 33 3 3 1 62 1 2 1. Printing of sheets without resin (tapwater: 20 French 31 ,5 3 6 21 hydrotimetric degrees) 15 g. of fibers are broken down.

ersion is brou ht to 2 1 so as to btain fon'nette 3.33 3.33 68.7 2.21 3.2 Dlsp g g/ o sheets of 2 g.

2. Printing of sheets with resin precursor (PAREZ 607 There is indicated in Table Vlll the results of resin precursor retention, the amount of introduced resin precursor being 2. 1 percent.

TABLE VIII Retention Retain resin, Millequivm il 5 alents of grams] Miiiequivalents C O OH I100 gra oi CEO/100 grams grams oi paste Percent responding to about 75 millequivalents of COOH/lOO g.

Therefore, bleachings by usual methods should be conducted so as to go near a carboxyl rate of about 75 millequivalents/ l 00 g.

There will be noticed that sheets obtained from oxidated cellulose fibers having melamine-formaldehyde resin precursors retained thereon show substantial increasing in breaking length in the conditioned and wet states.

What is claimed is:

l. A process for preparing cellulose fibers having a melamine-formaldehyde resin precursor fixed thereon which comprises A) oxidizing said cellulose fibers with an alkali metal periodate to form aldehyde groups in the 2and 3positions, and the aldehyde-containing cellulose fibers are then further oxidized with an alkali metal chlorite to form carboxyl groups in the 2 and 3 positions, and

B) reacting the resulting oxidized cellulose fibers with a melamine-formaldehyde resin precursor in an acid medium at a pH of from about 6.5 to about 3.

2. A process as claimed in claim 1 wherein the melamineforrnaldehyde resin precursor is trimethylolmelamine.

3. The cellulose fiber product of the process claimed in claim 1.

3 3 UNITED STATES PATENT OFFICE (JERTEFICATE OF CORRECTION Patent No. 3,657,066 Dated April 18, 1972 lnvemofls) Marcel Chene et al It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 32 "14 .45 Should be -l4 .55

Signed and sealed this 1st day of January 1974.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. RENE D. TEGTMEYER Attesting Officer Acting Commissioner of Patents 'PMSO v UNITED STATES PATENT OFFICE QERHHCATE OF CORRECTION Patent No. 3 657 O66 Dated April 18, 1972 lnventofls) Marcel Chene et al It is certified that error appears in the above-identified patent end that: said Letters Patent are hereby corrected as shown below:

Column 4, line 32, "14.45" should be "14.55

Signed and sealed this 1st day of January 1974.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. RENE D. TEGTMEYER Attesting Officer Acting Commissioner of Patents 

2. A process as claimed in claim 1 wherein the melamine-formaldehyde resin precursor is trimethylolmelamine.
 3. The cellulose fiber product of the process claimed in claim 